Answer:
About 340 miles was the distance traveled by tornado.
Explanation:
This example comes under the "expressions of distance" as the special case of subject-verb agreement which carries a singular verb. Whenever we talk about a period of time, a sum of money or a distance as subjects, it always carries a singular verb. For example:
1. 100 dollars is not a huge amount for him.
2. 25 kilometers is a great distance.
3. 2 hours passes so easily when I am with you.
